Field of the Invention
The present invention concerns a method of managing a power demand for the operation of a rotary wing pilotless aircraft equipped with an internal combustion engine.
It further concerns a rotary wing pilotless aircraft provided with a turboshaft engine for implementing this management method.
Technological Background
There are known rotary wing machines including a single power unit for driving at least one rotor of the rotary wing system.
Such a power unit is then rated to supply the necessary power to the machine in order to propel it and/or support it.
It is sometimes necessary for this power unit to be an internal combustion engine of the DIESEL engine type for applications where certain fuels such as petrol cannot be used.
Now, the DIESEL engine offer for the aeronautical market is very limited, which sometimes involves use on aircraft of motor vehicle engines—of great reliability—but the power of which is not always suited to the aircraft and/or the power density of which is generally limited.
Moreover, on a vertical take-off and landing drone, the power demand is often maximum in the take-off and hovering phases, which are of relatively short duration in many missions.
It is therefore often necessary to “boost” the initial power of the engine to achieve acceptable installed performance.
Adding a turbocharger to the existing engine is a solution generally used to apply additional power to the driveshaft.
This turbocharger makes it possible to feed boost air to the inlet of the pistons, thereby significantly increasing the power developed by the engine.
Modification of the injection laws is also a way of increasing the power of the engine.
In both these cases it is necessary to ensure that the limit parameters of the engine (turbocharger turbine inlet temperature, crankcase pressure) are not impacted by these modifications or that the latter authorize a minimum service life of the engine.
Such a solution may also require more costly modifications to the engine cooling system, seals, etc.
Be this as it may, it is found that these solutions may prove insufficient to assure optimum functioning of the rotary wing machine, the maximum power delivered by a DIESEL engine being variable and dependent on the altitude of the machine and the temperature conditions.
These maximum available power variations are sufficiently large that they have to be taken into consideration and a dynamic strategy defined.
Also known is the use on some aircraft of a thermal auxiliary power unit (APU).
Such auxiliary power units are generally used to supply power to auxiliary circuits such as hydraulic or pneumatic circuits and are never used to drive a gearbox of at least one rotor on a rotary wing aircraft.
Moreover, if the single power unit of the rotary wing machine fails, that machine having no redundant safety elements to take over without interruption of service, the machine crashes in an uncontrolled manner.
There is therefore a considerable requirement to guarantee that a rotary wing machine in service can land safely in the event of failure of its power unit.
The present invention aims to overcome the various drawbacks described above by proposing a method of managing a power demand to assure the operation of a drone type rotary wing machine that is of particularly simple design and particularly simple to operate, reliable and economical, and capable of taking into account dynamically the variations in the maximum power supplied by the main engine of that machine.
Another object of the present invention is such a method assuring recovery of the machine in the event of failure of its main power unit, the machine embodying no redundancy.
A further object of the invention is a rotary wing aircraft such as a vertical take-off and landing (VTOL) drone, the original layout of the propulsion system of which allows the implementation of this method of managing a power demand.